[beeforpork]

With all the optimisations being implemented in compilers today, it is impressive to see how this opportunity to optimise is missed. Put differently, compiler writers bother about optimisations that gain 0.1% performance in some special cases, but others that could gain 20% performance are not implemented.

Why? Is this optimisation particularly difficult to implement? Or is it just missed low-hanging fruit? It sure looks easy (like: rearrange expressions to keep the expression tree shallow and left-branching to avoid stack operations).

[acdha]

Compiler developers have tons of benchmarks which they run. I’d bet that this is as simple as not being significant in their test suite, with a good chance that it’s both not as simple as it might seem or that there are impacts on more complicated code which is in their benchmark suite or a big customer’s app.

[DannyBee]

The truth is that the hotspot computer is pretty old at this point and never really implemented a lot of good, robust, and thorough optimizations (I've read the source every year or two). It does some stuff and hopes for the best.

This is why there is a real commercial jvm market with azul.

[yifanl]

It's possible that they're working in the frame of mind that there aren't any low-hanging fruit left after so many years of compiler optimizations and forget to even try.